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Frans DG avatar image
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Frans DG asked hermione12 commented

Travel time operator: simulation model results not equal to hand calculation

Dear reader,

The issue: the travel time of my operator in the simulation model is not the same as my hand calculations. The operator has a speed of 1.11 m/s, acceleration of 0.44 m/s, and deceleration of 1 m/s. The model is set to meters and seconds.

I created a situation in which an operator has to travel from node A to node B. The distance traveled is 11.6 meters according to the operator's statistics. I used a Staytime activity in the dashboard to measure the time the operator travels. This was equal to 11.71 seconds.

However, if I calculate the travel time by hand, I get a travel time of 12.27 seconds. I used the following equation:

distance = 0.5*acceleration*(t1)^2 + speed*t2 + 0.5*deceleration*(t3)^2

I assumed a constant acceleration, therefore, t1 = 1.11 / 0.44 and t3 = 1.11 / 1. As for t2, this has been determined by dividing the remaining distance (distance when there was no acceleration) by 1.11 (the speed).

Since I assumed that the acceleration and deceleration are constant, the outcome of my hand calculations should be the shortest time possible, which is 12.27 seconds.

I could understand if the operator in the simulation model would take a little longer, for instance, if the acceleration and/or speed would not be constant. However, as I see it, the travel time in the simulation model can never be shorter than the hand calculation.

Can somebody please explain why this happens?

With kind regards,

Frans

FlexSim 20.1.2
operatorflexsim 20.1.2
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Ben Wilson avatar image Ben Wilson ♦♦ commented ·

Hi @Frans DG, was Allister Wilson's answer helpful? If so, please click the red "Accept" button on their answer. Or if you still have questions, add a comment and we'll continue the conversation.

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1 Answer

Allister Wilson avatar image
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Allister Wilson answered hermione12 commented

Presumably there's a problem with your test setup or the way you're measuring time, in the attached model an operator with the same acceleration / deceleration / speed as yours takes 12.27s to travel 11.6m as expected.

20201030_operator_travel_time.fsm


20201030-operator-travel-time.fsm (30.4 KiB)
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Frans DG avatar image Frans DG commented ·

This is odd. Indeed, in your model, it is working fine. In case I find the problem, I will add it to this post. It most likely has to do with the AutoCad drawing that I added to the model. Perhaps something went wrong with the scaling.

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hermione12 avatar image hermione12 commented ·
hey @Allister Wilson can you please share the same model in 20.0.0 version? It would be a great help!!
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Allister Wilson avatar image Allister Wilson hermione12 commented ·

Is there a reason you can't install a more recent version of FlexSim?
Nothing in that model requires a license to access, if that's what you were worried about.

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hermione12 avatar image hermione12 Allister Wilson commented ·
I am using Flexsim 20.0 version. I am not able to open the model. So I asked for the 20.0 version for your model so as to refer.
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